New measurements from NASA's Herschel Space Observatory have discovered water with the same chemical signature as our oceans in a comet called Hartley 2 (pictured at right). The image at bottom right is an artist's concept of a comet.

This 3-D image shows the region where NASA's Deep Impact mission sent a probe into the surface of comet Tempel 1 in 2005. This picture was taken six years after the Deep Impact collision. 3D glasses are necessary to view this image.

This image from the High-Resolution Instrument on NASA's EPOXI mission spacecraft shows part of the nucleus of comet Hartley 2. The sun is illuminating the nucleus from the right. A distinct cloud of individual particles is visible.

This image, one of the closest taken of comet Hartley 2 by NASA's EPOXI mission, shows many features across the comet's surface. The length of the comet is equal to the distance between the Capitol building and the Washington Monument in Washington.

This enhanced image, one of the closest taken of comet Harley 2 by NASA's EPOXI mission, shows jets and where they originate from the surface. There are jets outgassing from the sunward side, the night side, and along the terminator.

Comet Hartley 2 can be seen in glorious detail in this image from NASA's EPOXI mission. It was taken as the spacecraft flew by around 6:59 a.m. PDT (9:59 a.m. EDT), from a distance of about 700 kilometers (435 miles).

NASA's EPOXI mission took this image of comet Hartley 2 on Nov. 2, 2010. The spacecraft will fly by the comet on Nov. 4, 2010. The white blob and the halo around it are the comet's outer cloud of gas and dust, called a coma.

This artist's concept shows a view of NASA's EPOXI mission spacecraft during its Nov. 4, 2010 flyby of comet Hartley 2. The fluffy shell around the comet, called a coma, is made up of gas and dust that blew off the comet's core, or nucleus.

This image from NASA's EPOXI mission shows Hartley 2 moving across the background field of stars. The coma, or cloud of gas and dust around the comet, expands and brightens over this time period. Animation available at the Photojournal.